Restriction of vesicular stomatitis virus in a nonpermissive rabbit cell line is at the level of protein synthesis

Replication of vesicular stomatitis virus (VSV) is restricted in a line of rabbit cornea (RC-60) cells; less than one infectious particle is produced per infected cell. We show that VSV is blocked at the level of viral-specific protein synthesis. VSV proteins are synthesized early in infection but the rate of VSV protein synthesis declines rapidly as infection proceeds. At times when synthesis of VSV proteins is barely detectable, VSV mRNA is produced and polyribosome structures are present. The VSV mRNA recovered from the polysome region directs the synthesis of VSV proteins in an in vitro reticulocyte translation system. This suggests that protein synthesis is blocked at some step beyond the level of initiation possibly at the level of elongation. Coinfection with vaccinia virus converts RC-60 cells to a permissive host. In contrast to the abortive infection with VSV alone, VSV proteins are synthesized throughout the replication cycle in doubly infected cells. Vaccinia supplies a product essential for sustained protein synthesis in the abortive system. We have confirmed that the replication of genome length 42 S RNA does not occur at late times in the abortive infection. This lack of 42 S RNA replication is explained by the shut-off of VSV protein synthesis, since continuous protein synthesis is required for the replication of VSV 42 S RNA.